AS Daily A Level Physics question
A small ball is rolled horizontally off a lab bench at speed u. Air resistance is negligible and the bench height is unchanged. If the launch speed is doubled to 2u, which statement about (i) the time to hit the floor and (ii) the horizontal distance travelled before landing is correct?
Answer
The correct answer is B.
Correct: B — Time unchanged; horizontal distance doubles. A is wrong because horizontal speed does not affect the fall time, though doubling speed would double horizontal distance. B is correct because the time to fall depends only on height and g, while horizontal distance = speed × same time, so doubling speed doubles the range. C is wrong because the time does not halve when only horizontal speed changes, and the range would not stay the same. D is wrong because with the same fall time, increasing horizontal speed increases, not decreases, the horizontal distance.